Antiplatelet therapies are important to decrease the morbidity and mortality associated with Peripheral Arterial Disease (PAD) through the prevention of thrombus formation. Aspirin (ASA) is a readily available and affordable antiplatelet medication that can help reduce adverse cardiovascular events by up to 25%. However, 25-60% of PAD patients are "ASA insensitive" having a lower than normal ability to inhibit platelet aggregation after standard aspirin dosing. In a previous study conducted by our lab, we were able to demonstrate a methodology for personalizing antiplatelet therapy using two platelet function tests, Platelet Function Analyzer-100 (PFA 100) and Light Transmission Aggregometry (LTA). To investigate this methodology further, we would like to conduct a pilot study on two cohorts of patients, one population continuing with their current medications (81mg ASA), and a second group who will get personalized antiplatelet therapy using our methodology (81-325mg ASA). In this study, 150 PAD patients taking 81mg Aspirin therapy presenting for clinical follow-up, or in-patient intervention, in vascular clinics or the emergency room, will be recruited to our study. 75 patients will be randomly assigned undergo platelet analysis using PFA-200 and LTA, and will have their antiplatelet therapy personalized. Patients will then be followed up in order to see if the patients with personalized therapy have better platelet inhibition. This study will allow us to help personalize antiplatelet therapy in PAD patients, allowing for better patient outcomes and decreased adverse cardiovascular events.

Inclusion Criteria:

• Self-reported intake of either 81 mg of aspirin per day for 3 or more days
• Diagnosed with peripheral arterial disease

Exclusion Criteria:

• Alcohol ingestion 24 hours prior to blood draw
• Patients receiving glycoprotein (GP) IIb/IIIa antagonists
• Ingestion of a non steroidal anti-inflammatory drug 3 days prior to blood draw
• History of bleeding disorders
• Gastrointestinal bleeding
• Hemorrhagic stroke
• Allergy to aspirin or ticagrelor
• Pregnancy, thrombocytopenia anmia or leukopenia